Method of and apparatus for plating



April ,1938. R. N. BROWN. 15,6 6

METHOD OF AND APPARATUS FOR PLATING Filed Aug. 7,. 1933;;II;;;IIIIIIIIIIIIIIIII'IIIIIIIIIIIIII'III'IIIIIIIIIIIIIIIIIIIIIIIIII iR1751??? M atenterl Apr. 26, 1938 2,115,616 METHOD OF AND APPARATUS FORPLATING Robert N. Brown, Detroit, Mich, assignor to Packard Motor CarCompany, Detroit, Mich, a corporation of Michigan Application August 7v1933, Serial No. 683,968

Claims. (Cl.,204-5) This imention relates to a process of and apparatusfor plating articles.

It is sometimes desirable to plate articles so that the coating is ofvarying thicknesses. In order to obtain different thicknesses ofcoating, it has previously been necessary to subject the article to morethan one plating operation. This has been necessary because the articlemust be adjusted in its carrier to place the portion having a desiredthickness of coating in a relation where it will not again be submergedin the bath, or portions of the article must be covered with .paramn orsimilar material in order to prevent further coatingthereof if completesubmersion in the bath is resorted to. The multiple plating operationsor multiple handling of an article during plating is expensive andrequires time,

and it is an object of this invention to provide apparatus for carryingan. article during a single plating process so that different portionswill have coatings of different thicknesses.

Another object of the invention is to provide apparatus for holdingbolts submerged in a bath during a plating process so that the coatingdeposited on the head portion will be thicker than the coating depositedon the shank portion.

A further object of the invention is to provide an apparatus for holdingarticles during a plating process so that a portion of the article isshielded. in a manner such that it will receive a thinner coatingthanthe unshielded portion.

Still another object of the inventionis to provide a novel and improvedplating" process wherein the coating deposited on a submerged article isthinner on one portion than on another portion. 1

Other objects or the invention will appear from the followingdescription taken in connection with the drawing, which forms a part ofthis specification, and in which:

Fig. l is a sectional view of plating apparatus incorporating myinvention;

Fig 2 is a sectional view taken on line 2-4 of Fig. 1 with parts of theapparatus broken away.

Referring now to the drawing by, characters of reierence, -l0 representsan open top tank ior containing an electrolyte II which in this inastance is a chromic acid solution H2Cr04. Ex-

nects with a source of electricity, such as a battery l'l.

Extending across the .tank and resting on the top edges thereof is asupporting member having a copper core i8 surrounded by a layer ofinsulating material l9. Wiring 20 leads from the battery and. isconnected with the end of the supporting bar core by a connector 2!fastened by a set screw 22. Suspended from the bar and extending intothe electrolyte is a holder for an article to be plated, which in thisinstance is a bolt 23. The holder consists of a pair of partly insulatedwire members 24 having the upper ends extending through an opening inthe bar and fixed in contact with the core by a set screw 25. The wiresare of a length to extend into the acid bath when the bar is resting onthe tank and the lower end portions are bent to form resilientlycontacting fingers providing an opening 28 therebetween through whichthe shank of a bolt can be readily axially inserted or removed. Currentpasses from the bar core through the holder to the bolt so that it formsthe cathode.

When the above described apparatus is associated and the switch It isclosed, then the electrolyte is decomposed by the electric current andchrome adheres to the bolt. This plating will be of substantiallyuniform thickness on the entire bolts surface unless some provision ismade to lessen the deposit in certain areas.

In many instances, difierent thicknesses of plating on articles arenecessary or desirable. A thick heavy plating on a bolt head isdesirable because of repeated applications of a wrench thereto and, atthe same time, a considerably thinner plating on the bolt shank isdesirable ii retapping oi the threadsis to be avoided. Two thicknessesof plating have heretofore required multiple plating operations oradjustment of the article support after being submerged in the bath.

In order to obtain two thicknesses of plating on different surfaces ofan article without re moval from the bath or adjustment of the apparatusor the article during the process, I provide means'ior limiting theelectrolytic action in the bath adjacent the portions of thearticle toreceive the thinner coating. In the present instance, a shield isprovided around the shank of the bolt so that the electrolytic actionwill be less adjacent the shank than adjacent the head. The shieldvconsists of a cylindrical casing 21 formed of insulation material havingone end adjacent the wires 24 removable and formed with an opening 28aligned with the opening 28 so that the bolt shank can projecttherethrough. An arm 29 extends upwardly from this end of the cylinder,and'one endoi' a hanger in the form of a wire 30, is fixed in the arm.The other end of the hanger is fixed to the supporting bar and aninsulation sleeve 3| covers the portion of the hanger intermediate thearm and the bar.

Openings 32 are provided in'the cylinder shield which with the opening28 allow the electrolyte to flll the casing when submerged. The casing2! acts as a shield around the bolt shank which reduces the chemicalaction produced by the electric current as compared with that in thesurrounding bath. The degree to which such chemical action causesdeposition of chromium on the bolt shank is regulated by the size ornumber of openings, and thus the thickness of plating on the bolt shankrelative to the thickness of the plating on the bolt' head can beregulated as desired.

It will be seen that the apparatus herein described can .be submerged ina plating bathand that portions of an article carried thereby will becoated diflerent thicknesses without any further adjustment or repeatedprocess operation.

Although the invention has been described in connection with a specificembodiment, the principles involved aresusceptible of numerous otherapplications which will readily occur to persons skilled in the art. Theinvention is therefore to be limited only as indicated appended claims.

What I claim is:

1. Proceastor chrome plating bolts, comprising submerging a bolt as acathode in a chrome acid solutIomeneasin'g the bolt shank in a memberprovided with means permitting limited electrolytic action around thebolt shank, suspending an anode-in the zone of the bolt, and passingcurrent through the solution by means of said 40 bolt and anode to formdiflerent thicknesses of plating on the shank and head of the bolt.

2. An electrolytic apparatus comprising a reby the scope of theceptacle,an electrically conducting support adv ,iacent the top of saidreceptacle, an article enclosing member of non-conducting materialdepending from said support, said article enclosing member having ahorizontally extending chamber open at one end, and a pair of resilientfingers of conducting material electrically connected to said supportand disposed adjacent the open end of said chamber.

3. An electrolytic apparatus comprising a receptacle, an electricallyconducting support adliacent the top of said receptacle, an articleenclosing member oi! non-conducting material depending from' saidsupport, said article enclosing member having a horizontally extendingchamber open at one end, the walls of said chamber being perforated.

4. An electrolytic apparatus comprising a receptacle, an electricallyconducting support adjacent the top of said receptacle, an articleenclosing member of non-conducting material depending from said support,said article enclosing member having a horizontally extending chamberopen at one end; and a pair of resilient fingers of conducting materialelectrically connected to said support and disposed adjacent the openend of said chamber, said fingers being adapted to grip an articletherebetween and support said article partially within said chamber.

5. An electrolytic apparatus comprising a receptacle, an electricallyconducting support adjacent-the'top of said receptacle, an articleenclosing member of non-conducting material depending from said support,said article enclosing member having a horizontally extendingchamber'open at one end, a member having a central aperture and adaptedto partially close said open end of ,said chamber,- and articlesupporting means electrically connected to said support and disposedoutside of said chamber and adjacent said aperture.

" V ROBERT N. BROWN.

